In recent years, regular physical exercise has become a permanent part of the life of millions of Americans and this trend is continuing. With the advent of greater emphasis in physical fitness and exercise there has been a dramatic rise in musculoskeletal injuries, especially to the muscles of the hips, legs, and ankles. One reason for such injuries is the failure to recognize the importance of stretching the body muscles prior to and after exercising. Regular stretching of the body muscles increases both the flexibility and the range of motion of the muscles. Stretching also reduces a likelihood of injury by preparing the muscles, ligaments, and tendons for the stress of exercise.
Realizing the importance of stretching the muscles is not enough. The muscles must be stretched properly to avoid injury during the stretching exercise itself. To avoid overtaxing the muscles, gradual, static stretches should be used rather than dynamic, bouncing-type stretches. Moreover, the ideal way to stretch muscles is while the muscles are in a relaxed state, thereby maximizing the range of motion of the muscle while minimizing the likelihood of a muscle pull or other injury.
However, it is difficult for an individual to apply gradual, static stretch to muscles, especially the larger muscles of the legs, for example, the hamstring muscles. One common manner of stretching the hamstring muscles is to lie in a supine position with the leg to be stretched raised up in the air and the other leg on the ground/floor. Then, either the exerciser himself pulls the raised leg forwardly toward his head by grasping the back of his thigh with his hands or a second individual positioned in front of the exerciser pushes against the raised leg. As can be appreciated, it is difficult for either the exerciser or his assistant to apply a steady, safe load on the leg. Moreover, it is not possible to accurately apply the same force against the leg each time the hamstring muscles are stretched, thus the extent to which the muscles are stretched can vary considerably from day-to-day or time-to-time.
Various apparatus have been developed for stretching the leg muscles. One such type of apparatus utilizes a harness or strap to engage around the lower leg or foot of the exerciser while in a supine position. A cord attached to the strap is pulled by the individual to rotate the leg about the hip joint in the direction toward the individual's head. Examples of such exercise apparatus are disclosed by U.S. Pat. No. 3,834,694 and 4,456,249. One drawback of this type of exercise apparatus is that it is not possible to accurately apply small incremental loads to the leg. Further, such devices constantly apply a force to the leg rather than holding the leg in a desired orientation. As a result, the leg is not able to be relaxed and thus does not reach its maximum range of motion. It is known that after a muscle is stretched to or near its maximum level for a period of time, if a maximum contraction of the muscle is made and the muscle is then allowed to relax, the proprioceptive neuromuscular facilitation phenomenon occurs whereby a dip in the muscle stretch reflex occurs so that the muscle can be stretched somewhat further. Moreover, with such devices disclosed in the '694 and '249 patents, it is difficult if not impossible to stretch the leg through a quantifiable range of motion so that the individual can repeatedly apply the same level of stretch to a desired muscle.
In another type of apparatus, a motorized swing arm is strapped to the lower leg or lower arm to move the distal section of the limb through a range of motion about the knee or elbow joint, thereby to provide physical therapy to increase the range of motion in an elbow or knee joint that has reduced mobility. An example of this type of device is disclosed by U.S. Pat. No. 4,089,330. One drawback of this particular type of device is that it is large, cumbersome and too expensive for individuals to purchase for home use. Moreover, this type of device also places a constant load on the body limb rather than simply holding the leg in the desired position, thereby removing the possibility and fear of overstretching while in this stable position, and thus allowing the user to relax.